1. Field of the Invention
The present invention relates generally to spacecraft propellant replacement systems. More particularly, the present invention is related to the propellant cooling system on a spacecraft, such as a lunar or non-earth surface activity module or a crew exploration vehicle.
2. Description of the Related Art
Systems and devices used in space flight and exploration, such as non-Earth surface activity modules and other spacecraft, are continuously being researched and developed for various purposes. Surface activity modules, such as a lunar surface activity module, are filled with propellant on earth and then launched into space to perform a predetermined mission. Upon completion of the mission, the modules are left in space or returned back to earth for analysis, parts, and/or for updating and reuse.
Current surface activity modules and spacecraft that require propellant to perform certain tasks, such as flight control, flight translation or orientation through use of thrusters, or other propellant requiring tasks, are performance limited and restricted due to the limited amount of propellant available onboard. As such, many spacecraft are incapable of performing extended missions or missions that require a substantial amount of propellant consumption over a short duration of time.
In addition, there are vehicle weight and size restrictions and limitations, as well as significant costs associated with the launching of a vehicle, which are directly related to the amount of propellant that the vehicle is carrying onboard. The more propellant a vehicle is carrying, generally, the heavier the vehicle, the larger the vehicle, and the more propellant required and the higher the costs associated with the launch of that vehicle. Moreover, there are overall limitations upon which the launching of such a vehicle becomes impractical or infeasible.
Cryocoolers are used to maintain stored cryogenic propellant at a proper temperature present a particular problem in spacecraft design. Conventional cryocoolers are integrated into propellant tank cooling systems disposed proximate to the tank, typically located as close as possible to the thermal load. This arrangement conveniently ensures a secure thermal interface between the cooler and thermal load that maximizes cooling performance. Such cryocooler systems may also support long term (e.g. five or more years) on-orbit storage of cryogenic propellants. During resupply operations the cryocooler is discarded along with the empty propellant tanks. However, this approach is expensive because space qualified cryocoolers have higher development and manufacturing costs than the cryogenic propellant tanks they are designed to cool.
In view of the foregoing, there is a need for a cryocooler systems and methods that provide a cost effective propellant storage solution for spacecraft, particularly for long duration missions. Further, there is a need for such systems and methods for extended and repeated space flight explorations. There is also a need for such systems and methods to support space flight missions that require a significant amount of propellant.